GEE error when extracting image timestamp

Question

I have filtered Sentinel 2 images to get suitable cloud free images from the time period I require, however I cannot figure out how to extract the date from the images, but with my current code I get the error:

Date (Error) Date: Parameter 'value' is required.

//  Define the image collection 
var image = ee.ImageCollection(sent2
// filter to get only images in the date range we are interested in
    .filterDate("2018-05-01", "2018-07-30")
// filter by polygon
    .filterBounds(tiwi))
// sort the collection by cloud cover 
    .sort("CLOUD_COVERAGE_ASSESSMENT")
// select the first image i.e. the most cloud free image in the date range
    .min();

// print the image to the console.
    print("A Sentinel-2 scene:", image);


  // Define visualization parameters in a JavaScript dictionary for true colour rendering. Bands 4,3 and 2 needed for RGB.
    var trueColour = {
        bands: ["B4", "B3", "B2"],
        min: 0,
        max: 3000
        };

  // Add the image to the map, using the visualization parameters.
  Map.addLayer(image, trueColour, "true-colour image");

// Get the timestamp and convert it to a date.
var date = ee.Date(image.get('system:time_start'));
print('Timestamp: ', date);

Answer 1

Your problem lies elsewhere.

when you use .min() Reduces an image collection by calculating the minimum value of each pixel across the stack of all matching bands..

This does not find the image with the lowest "CLOUD_COVERAGE_ASSESSMENT"

Your code is nearly there, as in the .sort() you put the collection in order of your cloud coverage.

Just change your .min() to .first() and your code will work.

//  Define the image collection 
var image = ee.ImageCollection(sent2
// filter to get only images in the date range we are interested in
    .filterDate("2018-05-01", "2018-07-30")
// filter by polygon
    .filterBounds(tiwi))
// sort the collection by cloud cover 
    .sort("CLOUD_COVERAGE_ASSESSMENT")
// select the first image i.e. the most cloud free image in the date range
    .first();  // previously => .min();

Now you will have only one image and it will no longer be a collection. Your date parameter should work fine now.

======= to find the date of each image of the collection is a different question.